1. Field of the Invention
The present invention relates to a motion guide apparatus, such as a linear motion guide apparatus or a ball screw device, and more particularly to a motion guide apparatus including two movable members or a screw shaft and a ball nut movable relative to each other, and a ball circulating device attached to one of the two movable members for suitably circulating and guiding the ball bearing elements to move through an endless ball guiding passage in the ball screw device or between the two movable members.
2. Description of the Prior Art
Typical motion guide apparatuses, such as the linear motion guide apparatuses or the ball screw devices comprise two movable members rotatable or movable relative to each other, and a number of ball bearing elements disposed between the two movable members for facilitating the sliding movement between the two movable members, and one or more ball circulating elements attached to the ball nut and communicative with the helical groove portions of the screw shaft and the ball nut for forming an endless ball guiding passage in the ball screw device or between the two movable members and for slidably receiving a number of ball bearing elements.
For example, U.S. Pat. No. 6,089,117 to Ebina et al., and U.S. Pat. No. 6,286,383 to Shirai et al. disclose two of the typical ball screw devices each comprising a ball nut pivotally or rotatably coupled onto a screw shaft, and a helically running threaded channel provided between the screw shaft and the ball nut for receiving a number of loaded ball bearing elements and for facilitating the sliding movement between the screw shaft and the ball nut, and one or more ball circulating elements attached to the ball nut and communicative with the helical groove portions of the screw shaft and the ball nut for forming the endless helically running threaded channel in the ball screw device or between the screw shaft and the ball nut.
For suitably or smoothly guiding or circulating the ball bearing elements through the ball circulating channels in the tubular circulating elements, the tubular circulating elements each include four guide grooves formed through the length of each of the tubular circulating elements and communicative with the returning channels of the tubular circulating elements respectively for receiving or engaging with the flexible coupling members of the ball couplers that hold or support the ball bearing elements.
However, normally, the flexible coupling members of the ball couplers are snugly fitted and received or engaged with or between the gaps that are formed between the screw shaft and the ball nut and will be snugly contacted with the screw shaft and the ball nut such that the flexible coupling members of the ball couplers may be twisted by the screw shaft and the ball nut and such that the ball bearing elements may not be suitably guided to move through the ball running channel of the typical ball screw devices, particularly when the ball bearing elements and the flexible coupling members of the ball couplers are moved in a fast speed through the endless helically running threaded channel in the ball screw device or between the screw shaft and the ball nut.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional motion guide apparatuses or ball screw devices.